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compared with underlying and overlying sediments, indicat-
ing that the DC bed sediment accumulated rapidly. This
result is consistent with the inferred 1 year or less duration
of the
floods, as suggested by paleohydraulic and glaciolog-
ical modeling of the Lake Agassiz discharge [Clarke et al.,
2004]. The zones of elevated DC content contained reduced
concentrations of biogenic carbonate; thus, it was not possi-
ble to date the peaks of the DC intervals; instead, foraminif-
era were separated from sediments above and below each
interval and dated in order to bracket the age of the DC beds.
The age model adopted for core 19 (Figure 4) assumes
linear sediment accumulation between most dated levels, with
the beds of elevated DC interpreted to have been laid down
rapidly (see section 5.1). Sedimentation rates below 440 cm
in core 19 were nonlinear, progressively diminishing upward
Figure 5. Age-depth model for core HU84011-12P (dark gray
line). Age data from Table 2 are plotted as rectangles. The hori-
zontal dimensions of 14 cm (±7 cm) represent uncertainty due to
bioturbation which was measured in La Have Basin on the Scotian
Shelf using 210 Pb activity dating (J. Smith, Bedford Institute of
Oceanography, personal communication, 2000). The vertical di-
mensions are the calibrated 2 σ age ranges for 14 C dates. The
source material for dates is indicated by the rectangle labels: Fm,
foraminifera; and Pol, correlation by pollen from a dated lake
sediment record.
from extremely high rates at 880 cm. The dated levels in core
19 were determined, either directly by AMS 14 C dating of
monospecific foraminiferal samples or indirectly by correlat-
ing 14 C-dated DC beds in the adjacent core 07P, and then by
comparing core 19 to 14 C-dated onshore pollen records from
a lake (Compass Pond) along the Northeast Newfoundland
coast using the similarity of pollen profile features or pollen
zone boundaries. A similar methodology was used to develop
an age model for core 12 (Figure 5).
Figure 4. Age-depth model for core HU87033-19P (dark gray line).
The gray bands represent beds of DC settled from plumes of
suspended sediment arising from energetic outflows from Hudson
Strait. The thick bed of DC-labeled AG correlates to the Agassiz
floods. Note that the age-depth interpretation generally shows higher
sedimentation rates (steeper curves) in these zones than in adjacent
sediment layers. Age data from Table 2 are plotted as rectangles.
The horizontal dimension of 14 cm (±7 cm) represents uncertainty
due to bioturbation that was measured in La Have Basin on the
Scotian Shelf using 210 Pb activity dating (J. Smith, Bedford Institute
of Oceanography, personal communication, 2000). The vertical
dimensions are the calibrated 2 σ age ranges for 14 C dates. The
source material for dates is indicated by the rectangle labels: Pfm,
planktic foraminifera; Bfm, benthic foraminifera; and Pol, correla-
tion by pollen from a dated lake sediment record.
5. RESULTS
5.1. Palynomorph Concentrations
Concentrations of most categories of palynomorphs in core
19 (Figure 6) seem to reflect dilution by greater sedimentation
rates within the DC beds (especially the Agassiz (AG) DC
bed and the DC bed below). The presence of low-growing
tundra vegetation and subsequently low shrub vegetation
explains why pollen concentrations were low below the 5 m
level in core 19. Pollen concentrations began to increase
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